Sintering method



Jan.: 13, 1970 E A ANDERSON ET AL 3,489,550

SINTERING METHOD H hmHm United States Patent 3,489,550 SINTERING METHOD Edward A. Anderson, Thornton Township, Cook County,

and Lambert J. Kilboy, Worth Township, Cook County,

Ill., assignors to United States Steel Corporation, a corporation of Delaware Filed Jan. 9, 1967, Ser. No. 608,020 Int. Cl. C21b 1/10 U.S. Cl. 75-5 4 Claims ABSTRACT OF THE DISCLOSURE A method of sintering a combustible mixture including iron oxides on a traveling grate in which there is a bottom unsintered zone, an intermediate combustion zone and an upper partially sintered bed. The combustion zone progresses downwardly from the entry end of the grate and in order to eliminate a at spot in the combustion zone intermediate its ends, the partially sintered bed is fractured at a position where the unsintered zone reaches a temperature of approximately 212 F.

This invention relates to a sintering method and more particularly to an improvement in the method of sintering a combustible mixture including iron oxides. Such methods are disclosed in Pettigrew Patent No. 2,498,766 dated Feb. 28, 1950; and Monaghan Patent No. 3,043,677 dated July 10, 1962. In the methods disclosed in the patents and in similar methods a mixture of moistened iron oxide ines such as blast furnace flue dust, sinter returns and carbonaceous fuel are fed to a traveling grate. The upper surface of the resulting bed is ignited shortly beyond the point of feed and combustion air is drawn downwardly through the bed so as to provide a relatively thin combustion zone through the length of the bed at a progressively increasing depth. The sinter formed above the combustion zone is less permeable than the original burden mix and because of various conditions within the bed the combustion zone, intermediate its length, reaches a point where its rate of downward progression levels off for some distance and then continues downward until the entire depth of the bed is sintered. This condition, of course, requires a longer bed and/or more time to complete the sintering operation.

It is therefore an object of our invention to provide a sintering method wherein the combustion zone progresses downward at substantially the same rate at all points between the top and bottom of the bed until it reaches the bottom of the bed.

Another object is to provide such a method which speeds up the sintering operation.

These and other objects will be more apparent after referring to the following specification and attached drawing, in which:

FIGURE l is a schematic side elevation of apparatus used in practicing the invention;

FIGURE 2 is an enlarged view of a portionof FIG- URE 1 showing the sintering bed; and

FIGURE 3 is a plan view of the penetrating apparatus used in practicing the invention.

Referring more particularly to the drawing, reference numeral 2 indicates a sintering grate. A sinter feeder 4 is provided at the entry end of the grate and an ignition furnace 6 is provided at the exit end of feeder 4 above a permeable sinter bed B. Wind boxes 8 are provided below the bed B. A plenum chamber 10 receives air from the wind boxes 8. Finished sinter ows over a slide .12 onto a shaker screen 14. The parts so far described are conventional and may be as shown in either of the above mentioned patents. Also, a hood 16 and associated mechanism as shown in the Monaghan patent may be pro- ICC vided. In addition, a similar hood may be arranged over an additional length of the grate 2, but it is necessary that free space be provided above the grate intermediate its length Ifor a purpose which will appear later. The bed B has a sintered portion B1, a combustion `zone B2 and an un-sintered zone B3. As shown in chain lines in FIG- URE 2 the proiile of the combustion zone B2 when practicing the method as shown in the above patents has a liat portion intermediate its length. Extensive tests and study have shown that the moisture content of the unsintered portion of the bed at this point is at a maximum and that the permeability is at a minimum. The temperature of zone B3 increases from the entry to discharge end thereof and we have discovered that the temperature of zone B3 below this ilat portion of zone B2 is somewhat less than 212 F.

According to our invention we increase the permeability of the bed at a position immediately preceding the point where the unsintered portion of the bed reaches a temperature of approximately 212 F. by fracturing the partially sintered bed above the combustion zone at this position. This is preferably accomplished by providing a spiked roller 18 which rests on top of the bed B with its spikes 20 extending downwardly into the bed to a point slightly above the combustion zone. The roller 18 is undriven and is preferably mounted on supports 22 so that it can be moved longitudinally of the bed B on slides 24 to locate it in the desired position. The spikes 20 are spaced around the periphery of the wheel and are also spaced across the width thereof. They are of substantially uniform cross section throughout their length as shown, but this does not preclude a very slight taper or a pointed end.

In operation, sinter mix is fed through feeder 4 to form the bed B and is ignited by furnace 6. Contact of the roller 18 with the top of the sinter bed B will cause the roller 18 to rotate and the spikes 20 to penetrate the zone B1 of the bed for the majority of its depth. This increases the permeability of the bed and hence enables freer ow of air through the bed B at this point. As a result the combustion zone, instead of being dat at this point, will continue downward as shown by broken lines at B2 in FIGURE 2. This enables the sintering machine to be speeded up so as to produce more sinter or, when designing sintering machines for a specific capacity, the length of the bed may be decreased with resultant saving in capital cost. Also, when using the process of Monaghan more efficient utilization of the recovered dust is possible.

While one embodiment of our invention has been shown and described, other adaptations and modifications may be made without departing from the scope of the following claims.

We claim: l

1. In a sintering process wherein a mixture of iron oxide lines and carbonaceous fuel is formed as a generally horizontal moving bed of substantially uniform depth having a water moisture content, heat is applied to the top of the bed at the entry end thereof, and air is drawn downwardly through said bed so as to provide a relatively thin combustion zone through the length of a moving sinter bed at a progressively increasing depth with the temperature of the unsintered portion of the bed increasing from the entry to discharge end of the bed; the improvement comprising fracturing the partially sintered bed above the-combustion zone at a position approximately adjacent the point Where the un-sintered portion of the bed reaches a temperature of approximately 212 F.

2. The sintering process of claim 1 wherein the fracturing of the bed is accomplished by a rotatable un- Patented Jan. 13, 1970L 3 4 driven wheel resting on top of the moving bed with References Cited spikes on the wheel across the width thereof and around UNITED STATES PATENTS the Iperiphery thereof extending downwardly into said bed to a point slightly above said combustion zone. eelllleer 3. The s'intering process of claim 2 wherein the spikes 5 3361315 1/1968 Sheets; ";5 5 X are of substantially uniform cross section throughout the majority 0f their length. OSCAR R. VERTIZ, Primary Examiner 4. The sintering process of claim 1 wherein the partlally smtered bed 1s fractured a'bove the positron where G o PE RS Asslstant Kammer the percentage of moisture in the un-sintered portion of 10 l U.S. C1. X.R.

the bed is at a maxium. l 266-21 

